Overload relay with means to prevent automatic reset

ABSTRACT

A thermal overload relay is constructed so that it cannot be reset automatically regardless of the position of the reset slide. This is accomplished by loading a reclose spring as the reset slide is being depressed, and then releasing the spring energy suddenly to permit overtravel as the spring returns to its normal energy released position, with this overtravel being sufficient to drive the contact operating toggle mechanism overcenter in the circuit closing direction.

United States Patent 1 McClellan OVERLOAD RELAY WITH MEANS TO PREVENTAUTOMATIC RESET [75] Inventor: David P. McClellan, Bellefontaine,

Ohio

[73] Assignee: I-T-E Imperial Corporation, Spring House, Pa.

[22] Filed: July 1, 1974 [21] Appl. No.: 484,683

52 U.S.Cl. ..337/ 56;337/72 51 Int. cm ..H01H 71/16 [58] Field of Search337/66, 72, 56, 64, 348, 337/358 [56] References Cited UNITED STATESPATENTS 3,267,236 8/1966 Walters et al 337/56 Dec. 23, 1975 3,307,0022/1967 Cooper 337/72 X Primary Examiner-G. Harris Attorney, Agent, orFirm-Ostrolenk, Faber, Gerb & Soffen [5 7] ABSTRACT A thermal overloadrelay is constructed so that it cannot be reset automatically regardlessof the position of the reset slide. This is accomplished by loading areclose spring as the reset slide is being depressed, and then releasingthe spring energy suddenly to permit overtravel as the spring returns toits normal energy released position, with this overtravel beingsufficient to drive the contact operating toggle mechanism overcenter inthe circuit closing direction.

10 Claims, l7 Drawing Figures atent Dec. 23, 1975 Sheet 1 of 3 3,928,833

U.S. Patent Dec. 23, 1975 Sheet 2 of3 3,928,833

fICv': .44

65 h" 52 50 5f 50 5/52 a US. Patant Dec. 23, 1975 Sheet3of3 3,928,833

OVERLOAD RELAY WITI-I MEANS TO PREVENT AUTOMATIC RESET Motor controllersutilizing electromagnetic contac- 5 tors are usually provided withoverload relays for automatically opening the contactor control circuitresponsive to over-current conditions. Typically, an overload relay is aheat sensitive device having a spring-powered l overcenter togglecontact operating mechanism. In addition, this type of over-load relayincludes a manually operable reset slide for closing the overload relayafter clearance of over-current conditions. In one mode of operation,the reset slide is maintained in a depressed position so that theoverload relay will reset automatically.

However, there are many applications wherein automatic resetting iscontrary to intended operation. Under such circumstances it is necessaryto provide an overload relay that does not have the capability ofresetting automatically even if the reset slide is jammed, taped, orotherwise maintained in its depressed position.

In accordance with the instant invention, automatic resetting of theoverload relay is defeated by providing a construction in which apositive manual operation is required for each resetting. As the resetslide is depressed, a reclosing spring is loaded, and the energy storedtherein is released abruptly as the reset slide reaches the end of itsstroke. Release of this spring energy results in driving a reclosemember past its normal position momentarily. In this normal positionwith the spring energy dissipated, the reclose member is ineffective toclose the overload relay. However, overtravel of the reclose membercaused by abruptly releasing the stored energy of the spring will closethe overload relay.

Accordingly, a primary object of the instant invention is to provide anovel construction for a thermal overload relay.

Another object is to provide an overload relay that is incapable ofautomatic resetting.

Still another object is to provide an overload relay of this type thatrequires manual operation of the reset slide for each closing operation.

A further object is to provide an overload relay of this typeconstructed to utilize the overtravel of a spring-loaded device forimpact resetting of the overload relay.

These objects as well as other objects of this invention shall becomereadily apparent after reading the following description of theaccompanying drawings in which:

FIG. 1 is a side elevation of an overload relay constructed inaccordance with teachings of the instant invention, with the coverremoved to reveal the internal elements.

FIG. 2 is a plan view of the overload relay looking in the direction ofarrows 22 of FIG. 1.

FIG. 3 is a perspective illustrating the relationship of the resettingelements for the overload relay of FIG. 1.

FIGS. 4a through 4g are diagrams illustrating the positions of thereclose member and movable contact arm for various positions of thereset slide.

FIG. 5 is an exploded perspective illustrating the resetting elementsfor another embodiment of the instant invention.

FIGS. 6a through 6f are diagrams showing the relationship between thereclose member and movable contact arm of FIG. 5 for different positionsof the reset slide.

Now referring to the figures and more particularly to FIGS. 1 through4g. Thermal overload relay 10 is generally of the type described in U.S.Pat. No. 3,562,688, issued Feb. 9, 1971, to F. W. Kussy et al. for QuickTrip Overload Relay Heaters. More particularly, overload relay 10includes a molded housing divided along line 11 into base 12 and cover13 secured together by rivets 14. Disposed externally of housing 12, 13at the edge of opening 15 are spaced apart main circuit terminals l7,18, each of which is generally L-shaped. U-shaped heater unit 99 isdisposed within main cavity 16 and is provided with out-turned legs 97,98 having clearance apertures which receive screws 19 that removablysecure heater 99 to terminals 17, 18. Auxiliary wire grip 96 is mountedto an extension of terminal 17.

Also disposed within cavity 16 is main tripping bimetal 20 which is astriplike member having its upper end 21 welded to the offset upper endof formed stiff support strip 22. Bimetal 20 is interposed betweenheater 99 and support 22, with the main central portion of support 22extending generally parallel to heater leg 94. The central portion ofsupport 22 is provided with a threaded aperture that receives thethreaded portion of adjusting screw 23 having a large stud 24 disposedexternally of base 12 at one end thereof. Rotation of adjusting screw 23is effective to pivot the lower end of support 22 about abutment 26,above adjusting screw 23, as a pivot. Leaf spring 27 biases support 22clockwise about pivot 26 and in so doing biases adjusting screw head 24to the left against base 12. Thus, as screw 23 is turned to pivotsupport 22 counterclockwise with respect to FIG. 1, the upper end 21 ofbimetal 20 will pivot counterclockwise about abutment 26 as a center,thereby moving lower end 31 of main bimetal 20 to the right with respectto FIG. 1.

Reversely bent auxiliary bimetal 35 is secured by rivets 34 to the lowerend 31 of main bimetal 20. Free end 36 of auxiliary bimetal 35 isoperatively engaged with the right end 42 of translator bar 41 extendingthrough a notch therein. Bar 41 also includes a clearance notch forstationary contact member and main operating spring 46. The latter isoperatively engaged by left end 43 of bar 41 as the latter is moved tothe right with respect to FIG. 1 by the combined deflections of bimetals20, 35 as a result of heat generated by current flowing in heater 99.

One end of stationary contact member 45 extends externally of housing12, 13 at the bottom thereof to constitute plug-in stab 47, and theother end of member 45 is reversely bent and mounts stationary contact51. The latter is engageable by movable contact 52 mounted at the upperend of movable contact arm 50. The lower end of contact arm isbifurcated and is seated in notches 53 in upper surface of bifurcatedextension 54 of conducting element 55. Lower end 48 of element 55extends externally of base 12 through the lower end thereof andconstitutes a plug-in stab.

Main operating spring 46 is a coiled tension member secured at its upperend to contact arm 50 just below movable contact 52. The lower end ofspring 46 is secured to extension 56 of member 55, positioned below thelower end of contact arm 50. It should be obvious to those skilled inthe art that main operating spring 46 and movable contact arm 50 areconnected and operatively positioned to form a spring powered overcentertoggle mechanism for opening and closing cooperating contacts 51, 52with a snap action. Opening is accomplished automatically uponpredetermined movement of bar 41 to the right with respect to FIG. 1.Protrusion 59 extending inward from cover 13 provides a stop whichestablishes the open circuit position of contact arm 50. Manuallydepressible reset slide 60 is biased upward by wire spring 61 so as toproject above the upper end of housing 12, 13 and, as will hereinafterbe seen, is utilized to reclose contacts 51, 52.

Secured to reset slide 60 and extending downward from the lower endthereof is reclose member 62 con structed of spring material. As slide60 is manually depressed, the lower end 63 of reclose member 62 engagesand then rides along the inclined upper surface 64 of stationarydeflector 65, thereby deflecting the lower end of reclose member 62 tothe right with respect to FIG. 1. This deflection continues and becomesmore pronounced as the deflection of member 62 increases. At apredetermined point in the downward reset stroke of member 60, the lowerend 63 of member 62 moves below cam surface 64 and deflector 65 isaligned with clearance notch 66 in member 62. This permits release ofthe stored spring energy in member 62 causing lower end 63 thereof tosnap to the left with respect to FIG. 1 and in so doing end 63 engagesmovable contact arm extension 67 to pivot the latter counterclockwisewith respect to FIG. 1.

Because of the energy stored in reclose member 62, there is aconsiderable overtravel for end 63. That is, end 63 moves to the left ofits normal or rest position illustrated in FIG. 4a and in so doingdrives movable contact arm 50 to the left of its so-called neutralposition wherein spring 46 is centered so that it does not urge contactarm 50 to move toward either open or closed positions. When reclosemember 62 comes to rest with slide 60 held partway along its returnstroke, the former abuts the left end of deflector 65. Even in thisposition of reclose member 62 movable contact arm 50 is free to be onthe open circuit side of the neutral position for the toggle whichoperates movable contact arm 50.

FIGS. 4a through 4g illustrate the deflection of reclose member 62 forprogressive positions of reset slide 60 as it is being depressed andreleased from its depressed position. Thus, it is seen that even ifreset slide 60 is maintained in its fully depressed position of FIG. 4d,upon automatic opening of contacts 51, 52, the lower end 63 of reclosemember 62 will not move contact arm 50 to the circuit closing side ofthe toggle neutral position. Because of this a discrete operation ofreset slide 60 through its closing stroke is required in order to closecontacts 51, 52.

In the embodiment of FIGS. and 6a through 6g, arm 150, mounting movablecontact 152 at its upper end, is pivoted at its bifurcated lower endportions 153, 153 and is operated into circuit opening and closingpositions by an overcenter toggle mechanism including main operatingspring 146. By depressing reset slide 160 the lower cam surface 161 ofdeflector 162, at the lower end of reset slide 160, engages inclinedsurface 163 at the right end of reclose member 164 moving the latter tothe left. When this occurs, coiled compression spring 165 is loaded andthis loading continues until the upper end of cam surface 161 passesbelow reclose member 164 at which time the energy stored in spring 165is suddenly released driving member 164 to the right with respect toFIG. 5. Because of kinetic energy positioning spring 166 is partlycompressed and spring 165 expands beyond its normal at-rest position.This permits reclose member 164 to drive contact arm to the right of theneutral position of the toggle mechanism so that spring 146 is theneffective to bring movable contact 152 into engagement with stationarycontact 172.

Thus, it is seen that the instant invention provides constructions forthermal overload relays which prevent automatic resetting regardless ofthe position of the reset slide.

Although in the foregoing preferred embodiments have been discussed,many variations and modifications will now become apparent to thoseskilled in the art, and it is therefore understood that this inventionis not limited by the disclosure but only by the appending claims.

The embodiments of the invention in which an exclusive privilege orproperty is claimed are defined as follows:

1. An overload relay including a stationary contact, a movable contactmounted for movement between a first position engaged with saidstationary contact and a second position separated from said stationarycontact, a repositionable overcenter spring means connected to saidmovable contact to bias the latter to said first position when saidmovable contact is on one side of a neutral position and to bias saidmovable contact to said second position when said movable contact is onthe other side of said neutral position, over-current responsive meansoperative upon the occurrence of predetermined overload conditions toautomatically operate said movable contact to said second position, amanual operating member operable in a reset stroke to reset said movablecontact to said first position, a reclose member, biasing means normallymaintaining said reclose member in a rest position on said other side ofsaid neutral position, deflector means operatively positioned to engagesaid reclose member as said operating member is operated to move in saidreset stroke, with engagement of said deflector means and said reclosemember moving the latter and thereby loading said biasing means, saiddeflector means and said operating means being constructed so thatoperative engagement thereof is broken abruptly when said operatingmember reaches a predetermined point in said reset stroke whereby energystored in said biasing means is released moving said reclose member intoengagement with said movable contact to drive the latter to said oneside of said neutral position from which point said spring means closessaid contacts.

2. An overload relay as set forth in claim 1 in which the deflectormeans is stationary, said biasing means is mounted to said operatingmember, and said reclose member is mounted to said operating member.

3. An overload relay as set forth in claim 2 in which the biasing meansand the reclose member are portions of a common member.

4. An overload relay as set forth in claim 3 in which the common memberextends from one end of the operating member and generally in thedirection of movement for the operating member in its said reset stroke.

5. An overload relay as set forth in claim 4 in which the common memberis elongated and is constructed of spring sheet stock, said deflectormeans including a cam surface that engages the reclose member and dementgenerally at right angles to movement of the operating member.

9. An over-load relay as set forth in claim 8 in which the deflectormeans and the reclose memberinclude cam formations that engage duringmovement of the operating member in the reset stroke to move the reclosemember away from the neutral position on the other side thereof.

10. An overload relay as set forth in claim 9 in which the operatingmember is biased in a first direction and movement thereof in said resetstroke is in a direction opposite to the first direction.

1. An overload relay including a stationary contact, a movable contactmounted for movement between a first position engaged with saidstationary contact and a second position separated from said stationarycontact, a repositionable overcenter spring means connected to saidmovable contact to bias the latter to said first position when saidmovable contact is on one side of a neutral position and to bias saidmovable contact to said second position when said movable contact is onthe other side of said neutral position, over-current responsive meansoperative upon the occurrence of predetermined overload conditions toautomatically operate said movable contact to said second position, amanual operating member operable in a reset stroke to reset said movablecontact to said first position, a reclose member, biasing means normallymaintaining said reclose member in a rest position on said other side ofsaid neutral position, deflector means operatively positioned to engagesaid reclose member as said operating member is operated to move in saidreset stroke, with engagement of said deflector means and said reclosemember moving the latter and thereby loading said biasing means, saiddeflector means and said operating means being constructed so thatoperative engagement thereof is broken abruptly when said operatingmember reaches a predetermined point in said reset stroke whereby energystored in said biasing means is released moving said reclose member intoengagement with said movable contact to drive the latter to said oneside of said neutral position from which point said spring means closessaid contacts.
 2. An overload relay as set forth in claim 1 in which thedeflector means is stationary, said biasing means is mounted to saidoperating member, and said reclose member is mounted to said operatingmember.
 3. An overload relay as set forth in claim 2 in which thebiasing means and the reclose member are portions of a common member. 4.An overload relay as set forth in claim 3 in which the common memberextends from one end of the operating member and generally in thedirection of movement for the operating member in its said reset stroke.5. An overload relay as set forth in claim 4 in which the common memberis elongated and is constructed of spring sheet stock, said deflectormeans including a cam surface that engages the reclose member anddeflects the latter away from the neutral position on the other sidethereof.
 6. An overload relay as set forth in claim 5 in which theoperating member is biased in a first direction and movement thereof insaid reset stroke is in a direction opposite to the first direction. 7.An overload relay as set forth in claim 1 in which the deflector meansis mounted to the handle and movable therewith.
 8. An overload relay asset forth in claim 7 also including means mounting the reclose memberfor movement generally at right angles to movement of the operatingmember.
 9. An overload relay as set forth in claim 8 in which thedeflector means and the reclose member include cam formations thatengage during movement of the operating member in the reset stroke tomove the reclose member away from the neutral position on the other sidethereof.
 10. An overload relay as set forth in claim 9 in which theoperating member is biased in a first direction and movement thereof insaid reset stroke is in a direction opposite to the first direction.